Offset composition



Patented Jan. 3, 1939 UNITED STATES OFFSET COMPOSITION Edmond H. Buoy, Stamford, Conn., assignor to Atlas Powder Company, Wilmington, Del., a

corporation of Delaware No Drawing. Application March 30, 1937, 1 Serial No. 133,927

6 Claims.

The present invention relates generally to the art of preventing offset upon freshly printed sheets, and is more particularly concerned with a medium to be employed for such purposes.

This application is a continuation in part of my copending application, Serial No. 582,919, filed December 24, 1931, forOffset process, and issued April 2'7, 1937, as Patent No. 2,078,790.

When printed or lithographed sheets, as they emerge from the press, are piled or superposed one upon another before the ink upon the last printed sheet is dry, the contact of one sheet with the undried ink upon a freshly printed sheet tends to produce a condition that is commonly known as oifset.

It has been the practice, therefore, in certain lines of printing or lithographing, where offsetting must be prevented, to spray, the sheets with an sheet. The substances mentioned are normally in a solid state at room temperatures and made. fiuidb'y heat, such fluid being then sprayed upon scription.

the sheets by'the use of. compressed air or the like; The airserves to breakup theQfluidinto minute particles and these particles thensolidify I or regain their original state when deposited uponv the 'sheets. l

I provide, according to the present invention, an anti-offsetting medium that is normally in a fiuid'state and .which may be sprayed upon a printed or lithographed sheet to form solid par-v ticles or lands"for spacing thepiled-up sheets apart "sumciently to prevent offsetting. This medinm comprises, in a preferred form, a soluble material or solute carried in a suitable evaporable or volatile solvent. In such solution theremay also be incorporated, if desired, any suitable plasticizers and any suitable inert fillers or extenders which will serve to give flatness or non-lightreflecting character to the solid particles deposited upon the sheets. Contra-distinguished from prior anti-oifsetting media, theinstant medium comprises a solution normally in a fluid state at room temperature, When the solution is sprayed upon the sheets the solvent of the solution quick- 1y evaporates. This evaporation occurs during the travel of the spray, as well as after striking the sheets, and thereby the solute or soluble material of the solution arrives upon the sheets in minute particles, which are sufficiently sticky or adherent when they arrive upon the sheets to remain and form, then or shortly thereafter, spacers of sufficient thickness to secure the desired result. Preferably, the surface tension of the particles or droplets should be great enough so that 10 the particles retain, to a useful extent,'the globular form for the purpose'of forming spacers of maximum height and minimum content.

The material or medium may be applied by any of the known methods of spraying, i. e., pneumatic, mechanical or hydraulic, the object in each case being the formation and projection of a fine spray of particles of a size great enough to provide the desired projections.

There are a number of advantages accruing to the use of the medium of my invention. The method may be carried out at less expense; it does not heat up the press room; the amount applied may be varied widely without objectionable effects; the material has much'greater adhesive characteristics; and it does not cloud the printed sheets nor render them greasy to the touch. As-the material whichI apply adheres more .firmly, the printed sheet is cleaner and more brilliant. Other features-and 'advantagesof the inven tion will appear from the following detailed de-- v To practice-the invention, Iprovide asolution in which the solute, comprising .anyone or more of the cellulose esters, is carried; in a suitable volatile solvent. These esters may, for example, consist of cellulose derivatives, such as cellulose nitrate and cellulose acetate, and are characterized by the fact that they are deposited from the sol- 40 vent in a tough film when thesolvent evaporates. These cellulose esters, therefore, form the solid particles or lands whichare deposited .upon the printed or lithographed sheets when the solventj evaporates. The solvent in which the cellulose esters are carried preferably consists Of-li. mixture of volatile substances, such as, for example,

j toluol,. xylol, alcohol, ethyl acetate, ethylene dichloride, butyl acetate, fCellosolve (monoethyl ether of ethylene glycol), acetone, ethyl lactate, carbon tetrachloride, one or more of the constituents of the mixture being a solvent for the cellulose ester either alone or when admixed with oneof the other volatile constituents of the solvent mixture. Other liquids which have a or relatively low boiling point and high vapor pressure, and will thus quickly evaporate and which are solvents for cellulose esters or are compatible with cellulose ester solutions may be employed. In order to give plasticity as well as binding characteristics to the particles or lands which are deposited upon the printed sheets, various plasticizers such, for example, as dibutyl phthalate, diethyl phthalate, tricresyl-phosphate, blown castor oil, camphor, or any of the other plasticizers which are suitable may be included in the solution if desired. Also, inert fillers or extenders of organic soaps such as aluminum stearate, aluminum palmitate, or zinc stearate may, if desired, be included in the solution to give the requisite flatness of surface or nonlight-reflecting characteristics to the particles or lands when they solidify. In this connection, further inert fillers may also comprise such fillers as asbestine or diatomaceous earth, fuller's earth, magnesium carbonate, or any other material which would be suitable for such purpose. The following are some examples of offsetting media employing the above described solutes and solvents in accordance with my invention, it being understood that these are given only in illustration and are in no way limitative:

One or more additional solutes which might be employed without departing from the present invention would consist of such solutes as other cellulose esters, cellulose ethers, phenolic base synthetic resin, glycol phthalate base or other natural or synthetic resin base materials of proper hardness and drying time suspended in an appropriate volatile solvent such as, for example, petroleum naphtha, toluol, or any other series of solvents. Even a wax, when dissolved in a suitable evaporable solvent, may be added without departing from the scope of the present invention.

It can be seen from the foregoing examples that the volatile solvent preferably comprises a mixture of a highly volatile, rapidly evaporative substance of the class of ethylene dichloride, alcohol, ethyl acetate, toluol, acetone and carbon tetrachloride with a less volatile, more slowly evaporable substance of the class of xylol, butyl acetate, monoethyl ether of ethylene glycol and ethyl lactate, at least one of said substances being a solvent for the cellulose ester. The solvent is preferably used in proportions of 4 to 9 parts of solvent mixture to 1 part of cellulose ester, and I have found that by using a solvent mixture in which from 10 to 30% of the mixture is of the less volatile, more slowl evaporable class of liquids listed above, the solution when sprayed will be a liquid as it is converted into a spray of globules, but as it travels through the atmosphere it will lose a sufficient fraction of volatile solvent to convert each globule into a self-sustaining adhesive particle which retains sufllcient solvent to adhere to the sheet. Each globule thereafter will be converted into a solid by evaporative loss of residual solvent and the solvent mixture above specified prevents blushing of the particles as they are converted into solid form to assure light transmitting quality and to prevent masking of the printing beneath them or alteration of the natural appearance to the eye of the unprinted portion of the sheet beneath them.

It is contemplated that the composition be employed with any of the mechanical methods, such as pressure, automatic or manually operable spraying mechanisms of well known types, for breaking up a solution of the above described ingredients into minute particles and spraying such particles upon the freshly printed sheets, or other sheets to be separated. To this end the solution of the above described ingredients will be prepared so as to have a consistency or viscosity that may be best handled by the spraying equipment employed, and capable of forming the desired spacing projections. Care must be taken not to let the spray become thick enough to merge the drops on the surface of the printed sheets, as the composition must be sprayed upon the sheets to form a plurality of discrete, small, raised particles.

As the volatile solvent of the solution begins to evaporate as soon as it is broken up or vaporized, the minute particles reach the printed sheets in a somewhat tacky and partially dry condition and dry completely immediately upon striking the sheet. Their exposed surfaces are then sufliciently hard and non-adhesive so that they act as solid particles that will not adhere to adjacent sheets.

As many apparently widely different embodi ments of my invention may be made without departing from the spirit and scope thereofyit is to be understood that I do not intend to limit myself to the specific embodiments thereof except as defined in the appended claims. It will be apparent that soluble solids, other than those above mentioned, may be employed, as well as a complete range of other solvents, plasticizers and inert fillers, without departing from the spirit of the present invention.

What I claim is:

1. A composition of matter for preventing oflset d of freshly printed sheets and which may be sprayed on freshly printed sheets to form thereon solid particles or lands, said composition being normally in the liquid state and comprising cellulose acetate, ethylene dichloride, alcohol, and ethyl lactate combined in substantially the proportions of one part of cellulose acetate, flve parts of ethylene dichloride, two and one-half parts of alcohol and one and one-tenth part of ethyl lactate.

2. A composition for spraying freshly printed sheets to prevent oiTsetting comprising a cellulose ester dissolved in a volatile solvent mixture therefor in proportion of from 4 to 9 parts solvent mixture to 1 part cellulose ester, said solvent mixture having a first component comprising a highly volatile, rapidly evaporative substance selected from the group consisting of toluol, ethylene dichloride, alcohol, ethyl acetate, acetone and carbon tetrachloride, and a second component comprising a less volatile, more slowly evaporable substance selected from the group consisting of xylol, butyl acetate, monoethyl ether of ethylene glycol and ethyl lactate, at

least one of said components being a solvent for the cellulose ester, and said second component being present in an amount of from 10 to 30% by weight of the solvent mixture, the composition having thecharacteristics (1) that it is liquid as its is converted into a spray of globules, (2) that as it travels through an evaporative atmosphere it loses a sufficient fraction of volatile solvent to converteach globule into a self-sustaining adhesive globule when it lands on a sheet, (3) that the globule adheres to the sheet while retaining solvent, (4) that the globule' thereafter is converted into a solid by evaporative loss of residual solvent, (5) that the globules in the aggregate maintain substantial identity and do not flow together in a film formation over the sheet, and (6) that in the aggregate the dried globules or lands are light-transmitting and substantially not glossy and do not indicate their presence on the sheet to the naked eye, or mask the printing beneath them, or alter the natural appearance to the eye of the unprinted sheet beneath them.

3. A composition of matter as set forth in claim 2 and wherein the cellulose ester is cellulose acetate.

4. A composition of matter as set forth in claim 2 and wherein the cellulose ester is nitrocellulose.

5. A composition of matter for preventing offset of freshly printed sheets and which may be sprayed'on freshly printed sheets to form thereon solid particles or lands, said composition being normally in the liquid state and comprising nitrocellulose, ethyl acetate, toluol, butyl acetate and monoethyl ether of diethylene glycol in substantially the following proportions:

Parts by weight Nitrocellulose 1.5

Ethyl ace 3.75

Toluol 1.8

Butyl acetate .93 Monoethyl ether of diethylene glycol 1 and a second component comprising a less volatile, more slowly evaporable substance selected fromthe group consisting of xylol, butylacetate,

monoethyl ether of ethylene glycol, and ethyl lactate, at least one of said components being a solvent for the cellulose ester, said second component being present in an amount of from 10 to by weight of the solvent mixture, and said solvent mixture being present in a proportion of from 4 to 9 parts of solvent mixture to 1 part of cellulose ester.

EDMOND H. BUCY. 

